/*
 * computer the number of trailing zeros in n factorial(n!)
 * 5*2 = 10;
 */
class TrailZeroFactorial{
	public static int numZeros(int num){
		int count = 0;
		if(num<0){
			System.out.println("Factorial is not defined less than 0!");
			return -1;
		}
		
		for (int i =5; num/i>0;i*=5){ // num/i is converted to int, so = 0 if num < i
			count +=num/i;
		}
		return count;
	}
	
	public static void main(String[] args){
		System.out.println(numZeros(26));
	}
}